If you take a sailboat out to the ocean overnight, what do you do to stay put?

There is something called a sea anchor (there are probably other names for it) and you can use it when you cannot anchor to the bottom. It does NOT make you stay in one place, but it will make your boat turn into the waves automatically. It can basically be just a large canvas bucket without a bottom. You can buy them. I've never used one, but I am pretty sure this is what they do.